Why does Macbeth kill King Duncan?
There are several reasons for his decision. Macbeth has been told by the witches that he will eventually become king. If Duncan is already king, how can Macbeth become king? Answer: kill Duncan. However, this is Macbeth's first mistake. The witches operate on the basis of fate--it is destined for Macbeth to become king. However, Macbeth takes matters into his own hands (rather than just letting events play out as they will), and that disrupts fate's system. (Or you can argue that it was fated that Macbeth would kill Duncan and that's what the witches were predicting when they said he's become king.)
Lady Macbeth also encourages Macbeth to kill Duncan. She is almost most status and power hungry than he is. She calls his manhood into questions, saying if he was a true man, he would do this. She uses all sorts of feminine manipulation to persuade him into killing Duncan--and Macbeth doesn't want to see like less of a man to his wife.
When the deed is actually to be committed, Lady Macbeth said she would have killed Duncan, but he looked too much like her father when he was asleep. Therefore, it leaves Macbeth to actually do the killing.
Here is a video summary of the play:
Macbeth kills Duncan becaide he tells his wife of the witches Prophecy and is convinced by lady macbeth that he must kill him in order to ptobe his manhood.
well, macbeth had a great oppurtunity to become a king but just didn't have enough patience.he made his own decisions as duncan was in his way
Nobody dislikes power, pelf and fame.Seeds of these aspirations enters into our physic and it grow bigger and bigger. When it sees the ripe time, acts for fruit. So was the case with Macbeth. There existed the seeds of the above aspirations in his heart. As soon as the witches predicted, those grew up and finally longed intensely for fruit. Such a person loses his conscience to judge what is right and wrong and finally his desires lead him to the wrong path and undertake any action for fulfilling his desires. Macbeth also became a victim of his evil desire and dreamt to grab the throne of Scotland by killing King Daucan. His wife Lady Macbeth worked as instigator like putting oil in a burning fire. In fine, circumstances compelled Macbeth to kill Duncan.
In ActI Sc3 the three witches prophecy that Macbeth,a general in King Duncan's army, will become the future king of Scotland,"All hail Macbeth,thou shalt be king hereafter!" Macbeth is indeed delighted to hear this prophecy and from this moment onwards becomes ambitious and decides to become the king of Scotland. However, he knows fully well that he can never become the King of Scotland legally, because Duncan has two sons who are his legal and rightful heirs. So he decides to murder Duncan, and his two sons because that is the only way by which he can become the King of Scotland.